If I can/could still play it today and find it immensely fun, then it's making the list for me (which unfortunately means no CoD games can get on this list, even though I enjoyed them at the times I played them):
Castlevania 1 (I don't need any other game from that generation)
Guilty Gear XX Accent Core Plus R
Sonic Adventure 2
Metal Gear Solid 2
Fable: The Lost Chapters
Star Wars: Knights of the Old Republic 1 & 2
Pillars of Eternity
Frozen Synapse
Fallout: New Vegas
Timesplitters 2
Tales of Symphonia
Kingdom Hearts 2
Final Fantasy: Crystal Chronicles
Soul Calibur 2
Monster Hunter
Muramasa: Rebirth (This translation is far superior to the original.)
Pokemon: Crystal Version
Golden Sun
Metroid Prime
Metroid Prime 2: Echoes
Metroid Prime 3: Corruption
Metroid Fusion
Yu-Gi-Oh! GX - Duel Academy
Stardew Valley
Kirby's Air Ride
Halo: Combat Evolved
Halo 3
DmC: Devil May Cry (& Virgil's Downfall)
Prototype
Civilization V (with Expansions)
Honorable mention to Star Fox Adventures, which I randomly decide to replay through every other year...